Phenylhydrazine hydrochloride → 2-(4-Methoxyphenyl)-1,2,3,4-tetrahydrocyclopenta[b]indole

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Reaction Steps

A mixture of 3-(4-methoxyphenyl)-1-cyclopentanone (15.21 g) and phenylhydrazine hydrochloride (11.56 g) in glacial acetic acid (110 ml) under nitrogen was stirred magnetically and slowly heated to 90° with a heating mantle. A white precipitate, which formed at approximately 60°, dissolved to give a red solution as the temperature rose exothermically to 110°. As soon as the solid had dissolved, the heating mantle was removed and the temperature allowed to return to 90°. The temperature was then maintained at 90° for 1 hour. The cooled solution was poured into water (400 ml). After refrigeration under nitrogen overnight, the supernatant liquid was filtered. The filter pad and residual material were dissolved in dichloromethane and the solution was washed with saturated sodium bicarbonate solution. The dried (MgSO4) solution was evaporated to a syrup which was subjected to an oil pump vacuum; wt. 18.7 g. This material in dichloromethane was chromatographed on a column of silica gel prepacked in dichloromethane. Elution with dichloromethane afforded a mixture of the titled product and 1,2,3,4-tetrahydro-1-(4-methoxyphenyl)cyclopent[b]indole. After solvent removal, the residual yellow syrup was crystallized from ethanol-hexane to give the titled product as pale yellow crystals; wt. 5.14 g (24.4%), mp=108°-110°.

Provenance & Evidence